-LRB- CNN -RRB- -- A Missouri police officer shot and killed a teenager Tuesday night in Berkeley , Missouri , just 2 miles from the St. Louis suburb of Ferguson , where Michael Brown was killed by police , an event that set off protests across the country .

But even though both cases involve white officers and black teens , Berkley 's mayor said the incidents are not the same .

Surveillance video appears to show a person -- identified by police and his family as Antonio Martin , 18 -- pointing a gun at an officer in a gas station parking lot in Berkeley right before the officer fatally shot the teen , Berkeley Mayor Theodore Hoskins told reporters Wednesday .

St. Louis County Police released on YouTube videos from three different angles that captured parts of the scene .

The shooting led to a tense couple of hours at the station , where scuffles with police broke out -- and what appeared to be lit fireworks were thrown -- as scores of people gathered to see what happened in an area still emotional over the August 9 shooting of Michael Brown .

But Hoskins , who is black , said that this shooting can not be likened to Brown 's death , in part because unlike the Ferguson case , this one was captured on video and allegedly involves an armed teen .

`` We reviewed the video and it appears that there was a gun pointed at the officer before the officer fired , '' Hoskins said . It `` does not appear that the police officer initiated '' the incident , he said .

Hoskins promised a thorough investigation .

`` I will not tolerate brutality of any policeman on our citizens , '' Hoskins told CNN . He added that people can `` rest assured that I will investigate this independently and make a complete report to the community . ''

Gov. Jay Nixon issued a brief statement saying , `` The events in Berkeley are a reminder that law enforcement officers have a difficult , and often dangerous , job in protecting themselves and law-abiding citizens . ''

A small group of protesters marched along some roads , including a highway , on Wednesday night , with some help from police .

`` Police are actually blocking the intersections for the protesters , '' St. Louis Post-Dispatch reporter Nicholas J.C. Pistor tweeted .

Still , six to eight protesters were nevertheless arrested for blocking off part of I-170 in Berkeley , CNN affiliate KMOV reported .

Martin faced a series of criminal charges over the past 15 months according to KMOV , including assault , armed robbery , unlawful use of a weapon , armed criminal action and stealing . The station showed Martin 's tearful mother Toni Martin saying her son was `` trying to get his life back together . ''

Police : Officer was investigating alleged theft

County Police Chief Jon Belmar said the shooting was tragic , but stressed the teen pointed a gun `` straight out '' at the officer , who fired in self-defense .

`` I understand the emotions ... but I think we need to understand the context of what happens ... with these types of situations , '' Belmar , whose department is investigating the shooting , told reporters .

Belmar said the officer , a 34-year-old , six-year Berkeley police veteran , was responding to a report of a theft when he pulled into the parking lot of a Mobil gas station in Berkeley shortly before 11:15 p.m. .

He left his cruiser and talked to two men in the lot . Eventually , as the officer stood by the driver 's side tire of his cruiser , one of the men backed away from the cruiser 's passenger side headlight , then stepped forward again pointing a gun at the officer , Belmar said .

The officer , whom police did not name , lost balance and fell as he moved back in reaction , but managed to fire what investigators believe were three shots , hitting the gunman at least once , Belmar said .

The slain teen is not believed to have fired his weapon , a loaded 9 mm handgun that police recovered at the scene , Belmar said . Police later released a photo of the weapon .

Meanwhile , there was a shooting in St. Louis on Wednesday . CNN affiliate KMOV reported one person was shot to death and three were in critical condition . No other details were immediately available .

Surveillance video , but body camera was n't worn

In the Martin case , video released by authorities showed a second man nearby who fled when the shooting occurred . Authorities are looking to interview him .

Martin 's father , Jerome Green , said his son had indicated he was going out to meet his girlfriend and had not mentioned any other person who might be with them .

`` He was supposed to come home , '' Green said . `` We 're getting ready for the holiday ; everyone wanted to see him . My grandmother had n't seen him for a while . ''

The officer involved was given a body camera before he left for patrol , but he was n't wearing it during the shooting , possibly because he was distracted when a supervisor gave it to him earlier Tuesday , Belmar said .

Hoskins said this did n't bother him , in part because the city , with three cameras for its 31 officers , had just started training officers to use them .

The cruiser 's dashboard camera also was n't recording , because the car 's emergency lights had n't been activated , Belmar said . The officer will be placed on administrative leave until the investigation is completed .

Green said Martin lived with his parents , brother and sister .

Protest , scuffle

Protesters late Tuesday and early Wednesday gathered around an ethnically diverse group of dozens of police officers , who stood between them and the scene . People in the crowd screamed at police . Others spoke more calmly .

What looked like a firework exploded near a gas pump , scattering people and temporarily filling the area with thick , white smoke , video from CNN affiliate KMOV showed .

Four people were arrested on suspicion of assaulting officers , Belmar said . One police officer was sent to an emergency room after injuring himself while trying to get away from the firework , Belmar said .

Another officer was treated at a hospital after being hit in the head with a rock or a brick , Belmar said .

St. Louis Post-Dispatch photographer David Carson said some of the protesters damaged police cars . CNN showed images of one squad car with a large dent in its side .

KMOV video showed a white plume rising at another location down the street . Belmar said someone had tried to set a fire at a nearby store , but someone extinguished it .

Before sunup , protesters thinned out , and those remaining stood calmly behind police tape .

Tuesday 's incident came about a month after a St. Louis County grand jury declined to indict Ferguson Police Officer Darren Wilson for fatally shooting Michael Brown on August 9 .

Authorities said Brown , who was black , was n't armed at the time , but that he tried to take Wilson 's gun while the officer was in his vehicle during an encounter in Ferguson . Some witness accounts said Wilson left his car and eventually fired while Brown , 18 , had his hands up in surrender , but others disputed this . Police said Wilson fired in self-defense as Brown charged him .

Berkeley is a city of about 8,000 people flanked by St. Louis International Airport to the west and Ferguson to the east .

CNN 's John Branch , Sara Ganim , George Howell and Rick Martin contributed to this report .

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NEW : Berkeley police arrest 6-8 protestors for blocking highway

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Police help a small group of protesters cross intersections , reporter says

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Antonio Martin already faced charges alleging assault , armed robbery and more

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Authorities : Berkeley shooting is not comparable to Ferguson